drivers/tty/pty.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  *  Copyright (C) 1991, 1992  Linus Torvalds
   4  *
   5  *  Added support for a Unix98-style ptmx device.
   6  *    -- C. Scott Ananian <cananian@alumni.princeton.edu>, 14-Jan-1998
   7  *
   8  */
   9
  10 #include <linux/module.h>
  11 #include <linux/errno.h>
  12 #include <linux/interrupt.h>
  13 #include <linux/tty.h>
  14 #include <linux/tty_flip.h>
  15 #include <linux/fcntl.h>
  16 #include <linux/sched/signal.h>
  17 #include <linux/string.h>
  18 #include <linux/major.h>
  19 #include <linux/mm.h>
  20 #include <linux/init.h>
  21 #include <linux/device.h>
  22 #include <linux/uaccess.h>
  23 #include <linux/bitops.h>
  24 #include <linux/devpts_fs.h>
  25 #include <linux/slab.h>
  26 #include <linux/mutex.h>
  27 #include <linux/poll.h>
  28 #include <linux/mount.h>
  29 #include <linux/file.h>
  30 #include <linux/ioctl.h>
  31 #include <linux/compat.h>
  32 #include "tty.h"
  33
  34 #undef TTY_DEBUG_HANGUP
  35 #ifdef TTY_DEBUG_HANGUP
  36 # define tty_debug_hangup(tty, f, args...)      tty_debug(tty, f, ##args)
  37 #else
  38 # define tty_debug_hangup(tty, f, args...)      do {} while (0)
  39 #endif
  40
  41 #ifdef CONFIG_UNIX98_PTYS
  42 static struct tty_driver *ptm_driver;
  43 static struct tty_driver *pts_driver;
  44 static DEFINE_MUTEX(devpts_mutex);
  45 #endif
  46
  47 static void pty_close(struct tty_struct *tty, struct file *filp)
  48 {
  49         if (tty->driver->subtype == PTY_TYPE_MASTER)
  50                 WARN_ON(tty->count > 1);
  51         else {
  52                 if (tty_io_error(tty))
  53                         return;
  54                 if (tty->count > 2)
  55                         return;
  56         }
  57         set_bit(TTY_IO_ERROR, &tty->flags);
  58         wake_up_interruptible(&tty->read_wait);
  59         wake_up_interruptible(&tty->write_wait);
  60         spin_lock_irq(&tty->ctrl.lock);
  61         tty->ctrl.packet = false;
  62         spin_unlock_irq(&tty->ctrl.lock);
  63         /* Review - krefs on tty_link ?? */
  64         if (!tty->link)
  65                 return;
  66         set_bit(TTY_OTHER_CLOSED, &tty->link->flags);
  67         wake_up_interruptible(&tty->link->read_wait);
  68         wake_up_interruptible(&tty->link->write_wait);
  69         if (tty->driver->subtype == PTY_TYPE_MASTER) {
  70                 set_bit(TTY_OTHER_CLOSED, &tty->flags);
  71 #ifdef CONFIG_UNIX98_PTYS
  72                 if (tty->driver == ptm_driver) {
  73                         mutex_lock(&devpts_mutex);
  74                         if (tty->link->driver_data)
  75                                 devpts_pty_kill(tty->link->driver_data);
  76                         mutex_unlock(&devpts_mutex);
  77                 }
  78 #endif
  79                 tty_vhangup(tty->link);
  80         }
  81 }
  82
  83 /*
  84  * The unthrottle routine is called by the line discipline to signal
  85  * that it can receive more characters.  For PTY's, the TTY_THROTTLED
  86  * flag is always set, to force the line discipline to always call the
  87  * unthrottle routine when there are fewer than TTY_THRESHOLD_UNTHROTTLE
  88  * characters in the queue.  This is necessary since each time this
  89  * happens, we need to wake up any sleeping processes that could be
  90  * (1) trying to send data to the pty, or (2) waiting in wait_until_sent()
  91  * for the pty buffer to be drained.
  92  */
  93 static void pty_unthrottle(struct tty_struct *tty)
  94 {
  95         tty_wakeup(tty->link);
  96         set_bit(TTY_THROTTLED, &tty->flags);
  97 }
  98
  99 /**
 100  *      pty_write               -       write to a pty
 101  *      @tty: the tty we write from
 102  *      @buf: kernel buffer of data
 103  *      @c: bytes to write
 104  *
 105  *      Our "hardware" write method. Data is coming from the ldisc which
 106  *      may be in a non sleeping state. We simply throw this at the other
 107  *      end of the link as if we were an IRQ handler receiving stuff for
 108  *      the other side of the pty/tty pair.
 109  */
 110
 111 static ssize_t pty_write(struct tty_struct *tty, const u8 *buf, size_t c)
 112 {
 113         struct tty_struct *to = tty->link;
 114
 115         if (tty->flow.stopped || !c)
 116                 return 0;
 117
 118         return tty_insert_flip_string_and_push_buffer(to->port, buf, c);
 119 }
 120
 121 /**
 122  *      pty_write_room  -       write space
 123  *      @tty: tty we are writing from
 124  *
 125  *      Report how many bytes the ldisc can send into the queue for
 126  *      the other device.
 127  */
 128
 129 static unsigned int pty_write_room(struct tty_struct *tty)
 130 {
 131         if (tty->flow.stopped)
 132                 return 0;
 133         return tty_buffer_space_avail(tty->link->port);
 134 }
 135
 136 /* Set the lock flag on a pty */
 137 static int pty_set_lock(struct tty_struct *tty, int __user *arg)
 138 {
 139         int val;
 140
 141         if (get_user(val, arg))
 142                 return -EFAULT;
 143         if (val)
 144                 set_bit(TTY_PTY_LOCK, &tty->flags);
 145         else
 146                 clear_bit(TTY_PTY_LOCK, &tty->flags);
 147         return 0;
 148 }
 149
 150 static int pty_get_lock(struct tty_struct *tty, int __user *arg)
 151 {
 152         int locked = test_bit(TTY_PTY_LOCK, &tty->flags);
 153
 154         return put_user(locked, arg);
 155 }
 156
 157 /* Set the packet mode on a pty */
 158 static int pty_set_pktmode(struct tty_struct *tty, int __user *arg)
 159 {
 160         int pktmode;
 161
 162         if (get_user(pktmode, arg))
 163                 return -EFAULT;
 164
 165         spin_lock_irq(&tty->ctrl.lock);
 166         if (pktmode) {
 167                 if (!tty->ctrl.packet) {
 168                         tty->link->ctrl.pktstatus = 0;
 169                         smp_mb();
 170                         tty->ctrl.packet = true;
 171                 }
 172         } else
 173                 tty->ctrl.packet = false;
 174         spin_unlock_irq(&tty->ctrl.lock);
 175
 176         return 0;
 177 }
 178
 179 /* Get the packet mode of a pty */
 180 static int pty_get_pktmode(struct tty_struct *tty, int __user *arg)
 181 {
 182         int pktmode = tty->ctrl.packet;
 183
 184         return put_user(pktmode, arg);
 185 }
 186
 187 /* Send a signal to the slave */
 188 static int pty_signal(struct tty_struct *tty, int sig)
 189 {
 190         struct pid *pgrp;
 191
 192         if (sig != SIGINT && sig != SIGQUIT && sig != SIGTSTP)
 193                 return -EINVAL;
 194
 195         if (tty->link) {
 196                 pgrp = tty_get_pgrp(tty->link);
 197                 if (pgrp)
 198                         kill_pgrp(pgrp, sig, 1);
 199                 put_pid(pgrp);
 200         }
 201         return 0;
 202 }
 203
 204 static void pty_flush_buffer(struct tty_struct *tty)
 205 {
 206         struct tty_struct *to = tty->link;
 207
 208         if (!to)
 209                 return;
 210
 211         tty_buffer_flush(to, NULL);
 212         if (to->ctrl.packet) {
 213                 spin_lock_irq(&tty->ctrl.lock);
 214                 tty->ctrl.pktstatus |= TIOCPKT_FLUSHWRITE;
 215                 wake_up_interruptible(&to->read_wait);
 216                 spin_unlock_irq(&tty->ctrl.lock);
 217         }
 218 }
 219
 220 static int pty_open(struct tty_struct *tty, struct file *filp)
 221 {
 222         if (!tty || !tty->link)
 223                 return -ENODEV;
 224
 225         if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
 226                 goto out;
 227         if (test_bit(TTY_PTY_LOCK, &tty->link->flags))
 228                 goto out;
 229         if (tty->driver->subtype == PTY_TYPE_SLAVE && tty->link->count != 1)
 230                 goto out;
 231
 232         clear_bit(TTY_IO_ERROR, &tty->flags);
 233         clear_bit(TTY_OTHER_CLOSED, &tty->link->flags);
 234         set_bit(TTY_THROTTLED, &tty->flags);
 235         return 0;
 236
 237 out:
 238         set_bit(TTY_IO_ERROR, &tty->flags);
 239         return -EIO;
 240 }
 241
 242 static void pty_set_termios(struct tty_struct *tty,
 243                             const struct ktermios *old_termios)
 244 {
 245         /* See if packet mode change of state. */
 246         if (tty->link && tty->link->ctrl.packet) {
 247                 int extproc = (old_termios->c_lflag & EXTPROC) | L_EXTPROC(tty);
 248                 int old_flow = ((old_termios->c_iflag & IXON) &&
 249                                 (old_termios->c_cc[VSTOP] == '\023') &&
 250                                 (old_termios->c_cc[VSTART] == '\021'));
 251                 int new_flow = (I_IXON(tty) &&
 252                                 STOP_CHAR(tty) == '\023' &&
 253                                 START_CHAR(tty) == '\021');
 254                 if ((old_flow != new_flow) || extproc) {
 255                         spin_lock_irq(&tty->ctrl.lock);
 256                         if (old_flow != new_flow) {
 257                                 tty->ctrl.pktstatus &= ~(TIOCPKT_DOSTOP | TIOCPKT_NOSTOP);
 258                                 if (new_flow)
 259                                         tty->ctrl.pktstatus |= TIOCPKT_DOSTOP;
 260                                 else
 261                                         tty->ctrl.pktstatus |= TIOCPKT_NOSTOP;
 262                         }
 263                         if (extproc)
 264                                 tty->ctrl.pktstatus |= TIOCPKT_IOCTL;
 265                         spin_unlock_irq(&tty->ctrl.lock);
 266                         wake_up_interruptible(&tty->link->read_wait);
 267                 }
 268         }
 269
 270         tty->termios.c_cflag &= ~(CSIZE | PARENB);
 271         tty->termios.c_cflag |= (CS8 | CREAD);
 272 }
 273
 274 /**
 275  *      pty_resize              -       resize event
 276  *      @tty: tty being resized
 277  *      @ws: window size being set.
 278  *
 279  *      Update the termios variables and send the necessary signals to
 280  *      peform a terminal resize correctly
 281  */
 282
 283 static int pty_resize(struct tty_struct *tty,  struct winsize *ws)
 284 {
 285         struct pid *pgrp, *rpgrp;
 286         struct tty_struct *pty = tty->link;
 287
 288         /* For a PTY we need to lock the tty side */
 289         mutex_lock(&tty->winsize_mutex);
 290         if (!memcmp(ws, &tty->winsize, sizeof(*ws)))
 291                 goto done;
 292
 293         /* Signal the foreground process group of both ptys */
 294         pgrp = tty_get_pgrp(tty);
 295         rpgrp = tty_get_pgrp(pty);
 296
 297         if (pgrp)
 298                 kill_pgrp(pgrp, SIGWINCH, 1);
 299         if (rpgrp != pgrp && rpgrp)
 300                 kill_pgrp(rpgrp, SIGWINCH, 1);
 301
 302         put_pid(pgrp);
 303         put_pid(rpgrp);
 304
 305         tty->winsize = *ws;
 306         pty->winsize = *ws;     /* Never used so will go away soon */
 307 done:
 308         mutex_unlock(&tty->winsize_mutex);
 309         return 0;
 310 }
 311
 312 /**
 313  *      pty_start - start() handler
 314  *      pty_stop  - stop() handler
 315  *      @tty: tty being flow-controlled
 316  *
 317  *      Propagates the TIOCPKT status to the master pty.
 318  *
 319  *      NB: only the master pty can be in packet mode so only the slave
 320  *          needs start()/stop() handlers
 321  */
 322 static void pty_start(struct tty_struct *tty)
 323 {
 324         unsigned long flags;
 325
 326         if (tty->link && tty->link->ctrl.packet) {
 327                 spin_lock_irqsave(&tty->ctrl.lock, flags);
 328                 tty->ctrl.pktstatus &= ~TIOCPKT_STOP;
 329                 tty->ctrl.pktstatus |= TIOCPKT_START;
 330                 spin_unlock_irqrestore(&tty->ctrl.lock, flags);
 331                 wake_up_interruptible_poll(&tty->link->read_wait, EPOLLIN);
 332         }
 333 }
 334
 335 static void pty_stop(struct tty_struct *tty)
 336 {
 337         unsigned long flags;
 338
 339         if (tty->link && tty->link->ctrl.packet) {
 340                 spin_lock_irqsave(&tty->ctrl.lock, flags);
 341                 tty->ctrl.pktstatus &= ~TIOCPKT_START;
 342                 tty->ctrl.pktstatus |= TIOCPKT_STOP;
 343                 spin_unlock_irqrestore(&tty->ctrl.lock, flags);
 344                 wake_up_interruptible_poll(&tty->link->read_wait, EPOLLIN);
 345         }
 346 }
 347
 348 /**
 349  *      pty_common_install              -       set up the pty pair
 350  *      @driver: the pty driver
 351  *      @tty: the tty being instantiated
 352  *      @legacy: true if this is BSD style
 353  *
 354  *      Perform the initial set up for the tty/pty pair. Called from the
 355  *      tty layer when the port is first opened.
 356  *
 357  *      Locking: the caller must hold the tty_mutex
 358  */
 359 static int pty_common_install(struct tty_driver *driver, struct tty_struct *tty,
 360                 bool legacy)
 361 {
 362         struct tty_struct *o_tty;
 363         struct tty_port *ports[2];
 364         int idx = tty->index;
 365         int retval = -ENOMEM;
 366
 367         /* Opening the slave first has always returned -EIO */
 368         if (driver->subtype != PTY_TYPE_MASTER)
 369                 return -EIO;
 370
 371         ports[0] = kmalloc(sizeof **ports, GFP_KERNEL);
 372         ports[1] = kmalloc(sizeof **ports, GFP_KERNEL);
 373         if (!ports[0] || !ports[1])
 374                 goto err;
 375         if (!try_module_get(driver->other->owner)) {
 376                 /* This cannot in fact currently happen */
 377                 goto err;
 378         }
 379         o_tty = alloc_tty_struct(driver->other, idx);
 380         if (!o_tty)
 381                 goto err_put_module;
 382
 383         tty_set_lock_subclass(o_tty);
 384         lockdep_set_subclass(&o_tty->termios_rwsem, TTY_LOCK_SLAVE);
 385
 386         if (legacy) {
 387                 /* We always use new tty termios data so we can do this
 388                    the easy way .. */
 389                 tty_init_termios(tty);
 390                 tty_init_termios(o_tty);
 391
 392                 driver->other->ttys[idx] = o_tty;
 393                 driver->ttys[idx] = tty;
 394         } else {
 395                 memset(&tty->termios_locked, 0, sizeof(tty->termios_locked));
 396                 tty->termios = driver->init_termios;
 397                 memset(&o_tty->termios_locked, 0, sizeof(tty->termios_locked));
 398                 o_tty->termios = driver->other->init_termios;
 399         }
 400
 401         /*
 402          * Everything allocated ... set up the o_tty structure.
 403          */
 404         tty_driver_kref_get(driver->other);
 405         /* Establish the links in both directions */
 406         tty->link   = o_tty;
 407         o_tty->link = tty;
 408         tty_port_init(ports[0]);
 409         tty_port_init(ports[1]);
 410         tty_buffer_set_limit(ports[0], 8192);
 411         tty_buffer_set_limit(ports[1], 8192);
 412         o_tty->port = ports[0];
 413         tty->port = ports[1];
 414         o_tty->port->itty = o_tty;
 415
 416         tty_buffer_set_lock_subclass(o_tty->port);
 417
 418         tty_driver_kref_get(driver);
 419         tty->count++;
 420         o_tty->count++;
 421         return 0;
 422
 423 err_put_module:
 424         module_put(driver->other->owner);
 425 err:
 426         kfree(ports[0]);
 427         kfree(ports[1]);
 428         return retval;
 429 }
 430
 431 static void pty_cleanup(struct tty_struct *tty)
 432 {
 433         tty_port_put(tty->port);
 434 }
 435
 436 /* Traditional BSD devices */
 437 #ifdef CONFIG_LEGACY_PTYS
 438
 439 static int pty_install(struct tty_driver *driver, struct tty_struct *tty)
 440 {
 441         return pty_common_install(driver, tty, true);
 442 }
 443
 444 static void pty_remove(struct tty_driver *driver, struct tty_struct *tty)
 445 {
 446         struct tty_struct *pair = tty->link;
 447
 448         driver->ttys[tty->index] = NULL;
 449         if (pair)
 450                 pair->driver->ttys[pair->index] = NULL;
 451 }
 452
 453 static int pty_bsd_ioctl(struct tty_struct *tty,
 454                          unsigned int cmd, unsigned long arg)
 455 {
 456         switch (cmd) {
 457         case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
 458                 return pty_set_lock(tty, (int __user *) arg);
 459         case TIOCGPTLCK: /* Get PT Lock status */
 460                 return pty_get_lock(tty, (int __user *)arg);
 461         case TIOCPKT: /* Set PT packet mode */
 462                 return pty_set_pktmode(tty, (int __user *)arg);
 463         case TIOCGPKT: /* Get PT packet mode */
 464                 return pty_get_pktmode(tty, (int __user *)arg);
 465         case TIOCSIG:    /* Send signal to other side of pty */
 466                 return pty_signal(tty, (int) arg);
 467         case TIOCGPTN: /* TTY returns ENOTTY, but glibc expects EINVAL here */
 468                 return -EINVAL;
 469         }
 470         return -ENOIOCTLCMD;
 471 }
 472
 473 #ifdef CONFIG_COMPAT
 474 static long pty_bsd_compat_ioctl(struct tty_struct *tty,
 475                                  unsigned int cmd, unsigned long arg)
 476 {
 477         /*
 478          * PTY ioctls don't require any special translation between 32-bit and
 479          * 64-bit userspace, they are already compatible.
 480          */
 481         return pty_bsd_ioctl(tty, cmd, (unsigned long)compat_ptr(arg));
 482 }
 483 #else
 484 #define pty_bsd_compat_ioctl NULL
 485 #endif
 486
 487 static int legacy_count = CONFIG_LEGACY_PTY_COUNT;
 488 /*
 489  * not really modular, but the easiest way to keep compat with existing
 490  * bootargs behaviour is to continue using module_param here.
 491  */
 492 module_param(legacy_count, int, 0);
 493
 494 /*
 495  * The master side of a pty can do TIOCSPTLCK and thus
 496  * has pty_bsd_ioctl.
 497  */
 498 static const struct tty_operations master_pty_ops_bsd = {
 499         .install = pty_install,
 500         .open = pty_open,
 501         .close = pty_close,
 502         .write = pty_write,
 503         .write_room = pty_write_room,
 504         .flush_buffer = pty_flush_buffer,
 505         .unthrottle = pty_unthrottle,
 506         .ioctl = pty_bsd_ioctl,
 507         .compat_ioctl = pty_bsd_compat_ioctl,
 508         .cleanup = pty_cleanup,
 509         .resize = pty_resize,
 510         .remove = pty_remove
 511 };
 512
 513 static const struct tty_operations slave_pty_ops_bsd = {
 514         .install = pty_install,
 515         .open = pty_open,
 516         .close = pty_close,
 517         .write = pty_write,
 518         .write_room = pty_write_room,
 519         .flush_buffer = pty_flush_buffer,
 520         .unthrottle = pty_unthrottle,
 521         .set_termios = pty_set_termios,
 522         .cleanup = pty_cleanup,
 523         .resize = pty_resize,
 524         .start = pty_start,
 525         .stop = pty_stop,
 526         .remove = pty_remove
 527 };
 528
 529 static void __init legacy_pty_init(void)
 530 {
 531         struct tty_driver *pty_driver, *pty_slave_driver;
 532
 533         if (legacy_count <= 0)
 534                 return;
 535
 536         pty_driver = tty_alloc_driver(legacy_count,
 537                         TTY_DRIVER_RESET_TERMIOS |
 538                         TTY_DRIVER_REAL_RAW |
 539                         TTY_DRIVER_DYNAMIC_ALLOC);
 540         if (IS_ERR(pty_driver))
 541                 panic("Couldn't allocate pty driver");
 542
 543         pty_slave_driver = tty_alloc_driver(legacy_count,
 544                         TTY_DRIVER_RESET_TERMIOS |
 545                         TTY_DRIVER_REAL_RAW |
 546                         TTY_DRIVER_DYNAMIC_ALLOC);
 547         if (IS_ERR(pty_slave_driver))
 548                 panic("Couldn't allocate pty slave driver");
 549
 550         pty_driver->driver_name = "pty_master";
 551         pty_driver->name = "pty";
 552         pty_driver->major = PTY_MASTER_MAJOR;
 553         pty_driver->minor_start = 0;
 554         pty_driver->type = TTY_DRIVER_TYPE_PTY;
 555         pty_driver->subtype = PTY_TYPE_MASTER;
 556         pty_driver->init_termios = tty_std_termios;
 557         pty_driver->init_termios.c_iflag = 0;
 558         pty_driver->init_termios.c_oflag = 0;
 559         pty_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 560         pty_driver->init_termios.c_lflag = 0;
 561         pty_driver->init_termios.c_ispeed = 38400;
 562         pty_driver->init_termios.c_ospeed = 38400;
 563         pty_driver->other = pty_slave_driver;
 564         tty_set_operations(pty_driver, &master_pty_ops_bsd);
 565
 566         pty_slave_driver->driver_name = "pty_slave";
 567         pty_slave_driver->name = "ttyp";
 568         pty_slave_driver->major = PTY_SLAVE_MAJOR;
 569         pty_slave_driver->minor_start = 0;
 570         pty_slave_driver->type = TTY_DRIVER_TYPE_PTY;
 571         pty_slave_driver->subtype = PTY_TYPE_SLAVE;
 572         pty_slave_driver->init_termios = tty_std_termios;
 573         pty_slave_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 574         pty_slave_driver->init_termios.c_ispeed = 38400;
 575         pty_slave_driver->init_termios.c_ospeed = 38400;
 576         pty_slave_driver->other = pty_driver;
 577         tty_set_operations(pty_slave_driver, &slave_pty_ops_bsd);
 578
 579         if (tty_register_driver(pty_driver))
 580                 panic("Couldn't register pty driver");
 581         if (tty_register_driver(pty_slave_driver))
 582                 panic("Couldn't register pty slave driver");
 583 }
 584 #else
 585 static inline void legacy_pty_init(void) { }
 586 #endif
 587
 588 /* Unix98 devices */
 589 #ifdef CONFIG_UNIX98_PTYS
 590 static struct cdev ptmx_cdev;
 591
 592 /**
 593  *      ptm_open_peer - open the peer of a pty
 594  *      @master: the open struct file of the ptmx device node
 595  *      @tty: the master of the pty being opened
 596  *      @flags: the flags for open
 597  *
 598  *      Provide a race free way for userspace to open the slave end of a pty
 599  *      (where they have the master fd and cannot access or trust the mount
 600  *      namespace /dev/pts was mounted inside).
 601  */
 602 int ptm_open_peer(struct file *master, struct tty_struct *tty, int flags)
 603 {
 604         int fd;
 605         struct file *filp;
 606         int retval = -EINVAL;
 607         struct path path;
 608
 609         if (tty->driver != ptm_driver)
 610                 return -EIO;
 611
 612         fd = get_unused_fd_flags(flags);
 613         if (fd < 0) {
 614                 retval = fd;
 615                 goto err;
 616         }
 617
 618         /* Compute the slave's path */
 619         path.mnt = devpts_mntget(master, tty->driver_data);
 620         if (IS_ERR(path.mnt)) {
 621                 retval = PTR_ERR(path.mnt);
 622                 goto err_put;
 623         }
 624         path.dentry = tty->link->driver_data;
 625
 626         filp = dentry_open(&path, flags, current_cred());
 627         mntput(path.mnt);
 628         if (IS_ERR(filp)) {
 629                 retval = PTR_ERR(filp);
 630                 goto err_put;
 631         }
 632
 633         fd_install(fd, filp);
 634         return fd;
 635
 636 err_put:
 637         put_unused_fd(fd);
 638 err:
 639         return retval;
 640 }
 641
 642 static int pty_unix98_ioctl(struct tty_struct *tty,
 643                             unsigned int cmd, unsigned long arg)
 644 {
 645         switch (cmd) {
 646         case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
 647                 return pty_set_lock(tty, (int __user *)arg);
 648         case TIOCGPTLCK: /* Get PT Lock status */
 649                 return pty_get_lock(tty, (int __user *)arg);
 650         case TIOCPKT: /* Set PT packet mode */
 651                 return pty_set_pktmode(tty, (int __user *)arg);
 652         case TIOCGPKT: /* Get PT packet mode */
 653                 return pty_get_pktmode(tty, (int __user *)arg);
 654         case TIOCGPTN: /* Get PT Number */
 655                 return put_user(tty->index, (unsigned int __user *)arg);
 656         case TIOCSIG:    /* Send signal to other side of pty */
 657                 return pty_signal(tty, (int) arg);
 658         }
 659
 660         return -ENOIOCTLCMD;
 661 }
 662
 663 #ifdef CONFIG_COMPAT
 664 static long pty_unix98_compat_ioctl(struct tty_struct *tty,
 665                                  unsigned int cmd, unsigned long arg)
 666 {
 667         /*
 668          * PTY ioctls don't require any special translation between 32-bit and
 669          * 64-bit userspace, they are already compatible.
 670          */
 671         return pty_unix98_ioctl(tty, cmd,
 672                 cmd == TIOCSIG ? arg : (unsigned long)compat_ptr(arg));
 673 }
 674 #else
 675 #define pty_unix98_compat_ioctl NULL
 676 #endif
 677
 678 /**
 679  *      ptm_unix98_lookup       -       find a pty master
 680  *      @driver: ptm driver
 681  *      @file: unused
 682  *      @idx: tty index
 683  *
 684  *      Look up a pty master device. Called under the tty_mutex for now.
 685  *      This provides our locking.
 686  */
 687
 688 static struct tty_struct *ptm_unix98_lookup(struct tty_driver *driver,
 689                 struct file *file, int idx)
 690 {
 691         /* Master must be open via /dev/ptmx */
 692         return ERR_PTR(-EIO);
 693 }
 694
 695 /**
 696  *      pts_unix98_lookup       -       find a pty slave
 697  *      @driver: pts driver
 698  *      @file: file pointer to tty
 699  *      @idx: tty index
 700  *
 701  *      Look up a pty master device. Called under the tty_mutex for now.
 702  *      This provides our locking for the tty pointer.
 703  */
 704
 705 static struct tty_struct *pts_unix98_lookup(struct tty_driver *driver,
 706                 struct file *file, int idx)
 707 {
 708         struct tty_struct *tty;
 709
 710         mutex_lock(&devpts_mutex);
 711         tty = devpts_get_priv(file->f_path.dentry);
 712         mutex_unlock(&devpts_mutex);
 713         /* Master must be open before slave */
 714         if (!tty)
 715                 return ERR_PTR(-EIO);
 716         return tty;
 717 }
 718
 719 static int pty_unix98_install(struct tty_driver *driver, struct tty_struct *tty)
 720 {
 721         return pty_common_install(driver, tty, false);
 722 }
 723
 724 /* this is called once with whichever end is closed last */
 725 static void pty_unix98_remove(struct tty_driver *driver, struct tty_struct *tty)
 726 {
 727         struct pts_fs_info *fsi;
 728
 729         if (tty->driver->subtype == PTY_TYPE_MASTER)
 730                 fsi = tty->driver_data;
 731         else
 732                 fsi = tty->link->driver_data;
 733
 734         if (fsi) {
 735                 devpts_kill_index(fsi, tty->index);
 736                 devpts_release(fsi);
 737         }
 738 }
 739
 740 static void pty_show_fdinfo(struct tty_struct *tty, struct seq_file *m)
 741 {
 742         seq_printf(m, "tty-index:\t%d\n", tty->index);
 743 }
 744
 745 static const struct tty_operations ptm_unix98_ops = {
 746         .lookup = ptm_unix98_lookup,
 747         .install = pty_unix98_install,
 748         .remove = pty_unix98_remove,
 749         .open = pty_open,
 750         .close = pty_close,
 751         .write = pty_write,
 752         .write_room = pty_write_room,
 753         .flush_buffer = pty_flush_buffer,
 754         .unthrottle = pty_unthrottle,
 755         .ioctl = pty_unix98_ioctl,
 756         .compat_ioctl = pty_unix98_compat_ioctl,
 757         .resize = pty_resize,
 758         .cleanup = pty_cleanup,
 759         .show_fdinfo = pty_show_fdinfo,
 760 };
 761
 762 static const struct tty_operations pty_unix98_ops = {
 763         .lookup = pts_unix98_lookup,
 764         .install = pty_unix98_install,
 765         .remove = pty_unix98_remove,
 766         .open = pty_open,
 767         .close = pty_close,
 768         .write = pty_write,
 769         .write_room = pty_write_room,
 770         .flush_buffer = pty_flush_buffer,
 771         .unthrottle = pty_unthrottle,
 772         .set_termios = pty_set_termios,
 773         .start = pty_start,
 774         .stop = pty_stop,
 775         .cleanup = pty_cleanup,
 776 };
 777
 778 /**
 779  *      ptmx_open               -       open a unix 98 pty master
 780  *      @inode: inode of device file
 781  *      @filp: file pointer to tty
 782  *
 783  *      Allocate a unix98 pty master device from the ptmx driver.
 784  *
 785  *      Locking: tty_mutex protects the init_dev work. tty->count should
 786  *              protect the rest.
 787  *              allocated_ptys_lock handles the list of free pty numbers
 788  */
 789
 790 static int ptmx_open(struct inode *inode, struct file *filp)
 791 {
 792         struct pts_fs_info *fsi;
 793         struct tty_struct *tty;
 794         struct dentry *dentry;
 795         int retval;
 796         int index;
 797
 798         nonseekable_open(inode, filp);
 799
 800         /* We refuse fsnotify events on ptmx, since it's a shared resource */
 801         filp->f_mode |= FMODE_NONOTIFY;
 802
 803         retval = tty_alloc_file(filp);
 804         if (retval)
 805                 return retval;
 806
 807         fsi = devpts_acquire(filp);
 808         if (IS_ERR(fsi)) {
 809                 retval = PTR_ERR(fsi);
 810                 goto out_free_file;
 811         }
 812
 813         /* find a device that is not in use. */
 814         mutex_lock(&devpts_mutex);
 815         index = devpts_new_index(fsi);
 816         mutex_unlock(&devpts_mutex);
 817
 818         retval = index;
 819         if (index < 0)
 820                 goto out_put_fsi;
 821
 822
 823         mutex_lock(&tty_mutex);
 824         tty = tty_init_dev(ptm_driver, index);
 825         /* The tty returned here is locked so we can safely
 826            drop the mutex */
 827         mutex_unlock(&tty_mutex);
 828
 829         retval = PTR_ERR(tty);
 830         if (IS_ERR(tty))
 831                 goto out;
 832
 833         /*
 834          * From here on out, the tty is "live", and the index and
 835          * fsi will be killed/put by the tty_release()
 836          */
 837         set_bit(TTY_PTY_LOCK, &tty->flags); /* LOCK THE SLAVE */
 838         tty->driver_data = fsi;
 839
 840         tty_add_file(tty, filp);
 841
 842         dentry = devpts_pty_new(fsi, index, tty->link);
 843         if (IS_ERR(dentry)) {
 844                 retval = PTR_ERR(dentry);
 845                 goto err_release;
 846         }
 847         tty->link->driver_data = dentry;
 848
 849         retval = ptm_driver->ops->open(tty, filp);
 850         if (retval)
 851                 goto err_release;
 852
 853         tty_debug_hangup(tty, "opening (count=%d)\n", tty->count);
 854
 855         tty_unlock(tty);
 856         return 0;
 857 err_release:
 858         tty_unlock(tty);
 859         // This will also put-ref the fsi
 860         tty_release(inode, filp);
 861         return retval;
 862 out:
 863         devpts_kill_index(fsi, index);
 864 out_put_fsi:
 865         devpts_release(fsi);
 866 out_free_file:
 867         tty_free_file(filp);
 868         return retval;
 869 }
 870
 871 static struct file_operations ptmx_fops __ro_after_init;
 872
 873 static void __init unix98_pty_init(void)
 874 {
 875         ptm_driver = tty_alloc_driver(NR_UNIX98_PTY_MAX,
 876                         TTY_DRIVER_RESET_TERMIOS |
 877                         TTY_DRIVER_REAL_RAW |
 878                         TTY_DRIVER_DYNAMIC_DEV |
 879                         TTY_DRIVER_DEVPTS_MEM |
 880                         TTY_DRIVER_DYNAMIC_ALLOC);
 881         if (IS_ERR(ptm_driver))
 882                 panic("Couldn't allocate Unix98 ptm driver");
 883         pts_driver = tty_alloc_driver(NR_UNIX98_PTY_MAX,
 884                         TTY_DRIVER_RESET_TERMIOS |
 885                         TTY_DRIVER_REAL_RAW |
 886                         TTY_DRIVER_DYNAMIC_DEV |
 887                         TTY_DRIVER_DEVPTS_MEM |
 888                         TTY_DRIVER_DYNAMIC_ALLOC);
 889         if (IS_ERR(pts_driver))
 890                 panic("Couldn't allocate Unix98 pts driver");
 891
 892         ptm_driver->driver_name = "pty_master";
 893         ptm_driver->name = "ptm";
 894         ptm_driver->major = UNIX98_PTY_MASTER_MAJOR;
 895         ptm_driver->minor_start = 0;
 896         ptm_driver->type = TTY_DRIVER_TYPE_PTY;
 897         ptm_driver->subtype = PTY_TYPE_MASTER;
 898         ptm_driver->init_termios = tty_std_termios;
 899         ptm_driver->init_termios.c_iflag = 0;
 900         ptm_driver->init_termios.c_oflag = 0;
 901         ptm_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 902         ptm_driver->init_termios.c_lflag = 0;
 903         ptm_driver->init_termios.c_ispeed = 38400;
 904         ptm_driver->init_termios.c_ospeed = 38400;
 905         ptm_driver->other = pts_driver;
 906         tty_set_operations(ptm_driver, &ptm_unix98_ops);
 907
 908         pts_driver->driver_name = "pty_slave";
 909         pts_driver->name = "pts";
 910         pts_driver->major = UNIX98_PTY_SLAVE_MAJOR;
 911         pts_driver->minor_start = 0;
 912         pts_driver->type = TTY_DRIVER_TYPE_PTY;
 913         pts_driver->subtype = PTY_TYPE_SLAVE;
 914         pts_driver->init_termios = tty_std_termios;
 915         pts_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 916         pts_driver->init_termios.c_ispeed = 38400;
 917         pts_driver->init_termios.c_ospeed = 38400;
 918         pts_driver->other = ptm_driver;
 919         tty_set_operations(pts_driver, &pty_unix98_ops);
 920
 921         if (tty_register_driver(ptm_driver))
 922                 panic("Couldn't register Unix98 ptm driver");
 923         if (tty_register_driver(pts_driver))
 924                 panic("Couldn't register Unix98 pts driver");
 925
 926         /* Now create the /dev/ptmx special device */
 927         tty_default_fops(&ptmx_fops);
 928         ptmx_fops.open = ptmx_open;
 929
 930         cdev_init(&ptmx_cdev, &ptmx_fops);
 931         if (cdev_add(&ptmx_cdev, MKDEV(TTYAUX_MAJOR, 2), 1) ||
 932             register_chrdev_region(MKDEV(TTYAUX_MAJOR, 2), 1, "/dev/ptmx") < 0)
 933                 panic("Couldn't register /dev/ptmx driver");
 934         device_create(&tty_class, NULL, MKDEV(TTYAUX_MAJOR, 2), NULL, "ptmx");
 935 }
 936
 937 #else
 938 static inline void unix98_pty_init(void) { }
 939 #endif
 940
 941 static int __init pty_init(void)
 942 {
 943         legacy_pty_init();
 944         unix98_pty_init();
 945         return 0;
 946 }
 947 device_initcall(pty_init);